1. Field of the Invention:
This invention relates to offshore subsea well apparatus and in particular to a connector for connecting a tieback conductor to a wellhead located subsea.
2. Description of the Prior Art:
U.S. Pat. No. 4,343,495, Philippe C. Nobileau et al, Aug. 10, 1982, describes the need for running of tieback conductors from a platform deck to a subsea wellhead. The tubular connector utilizes a tapered guide funnel for initial stabbing and bearing surfaces which operate on the outside surface of the wellhead to force the conductor string into angular alignment with the wellhead under the influence of the weight of the conductor string. Seals located between the tieback connector and the wellhead are compressed with axial movement of the tieback connector, and thereafter a lock-down bushing engages internal running tool threads on the wellhead and clamps the wellhead without rotation of the conductor.
Such a tieback connector solves angular misalignment problems between the conductor and the wellhead when the conductor approaches the wellhead, and solves the problem of damage to the seals by the elimination of conductor rotation for makeup.
The tieback connector of the foregoing patent with its lock-down bushing, therein also referred to as a floating bushing, requires threads on the internal bore of the wellhead for makeup. In U.S. Pat. No. 4,696,493, Norman Brammer, Sept. 29, 1987, a tieback system is shown that is adapted to engage circumferential grooves in the wellhead, rather than internal threads in the wellhead. This tieback system utilizes a bushing having an inner and outer ring. The outer ring carries locking elements. The inner ring, when rotated downward, moves the locking elements out into engagement with the grooves.